Digital home electronic products, including cellular phones, flat panel displays, digital still cameras, and DVD recorders, have rapidly become widespread, and miniaturization and reduction in thickness of these devices are demanded. Using a more flexible substrate in the devices is an effective way to miniaturize and reduce the thickness of the devices, and the use of flexible printed circuit (FPC) boards shows a rapid increase. FPC boards are not only used as a simple circuit board, but also increasingly used as a functional module on which a semiconductor device, a microchip component, a connector, and the like are mounted.
Surface mount technology (SMT) is a widely used technique for mounting various electronic components such as an IC chip (bare chip), an electronic component module, and a passive element (chip component) onto a printed circuit board including an FPC board and a rigid printed circuit (RPC) board. In SMT, typically, after solder paste is printed on a printed circuit board, an electronic component is placed on the printed circuit board. Then, finally, the solder is melted by reflowing, and cured, thereby to electrically connect the electrode terminals of the electronic component and the wiring of the circuit board to each other (see, e.g., Patent Literature 1).